The proposed research initially seeks to obtain a cDNA clone for the regulatory sub-unit of rat cyclic-AMP-dependent protein kinase type I (RI) from a rat cDNA library which has been prepared from normal rat heart messenger RNA. This protein may be significant in investigating the molecular basis for hypertension in spontaneously hypertensive rats (SHR) because it is found at 4-fold reduced levels in SHR heart tissue as compared to normal rat (WKY) heart. After characterization of the cDNA clone by restriction mapping and DNA sequencing, it will be used as a probe to examine the levels of messenger RNAs for this protein in normal and spontaneously hypertensive rat heart tissue of various ages, S-1 nuclease protection mapping and also to screen the genomic DNAs from these two sources by digestion of the genomic DNAs with restriction endonucleases. This will determine gene frequency and may reveal different restriction patterns for SHR and WKY for this gene. Similar studies will also be carried out using a cDNA clone for rat cardiac myosin light chain 2 which has already been isolated from the rat cardiac cDNA library and partially characterized. Finally, genes for RI in SHR and WKY will be isolated by cloning genomic DNA fractions or by screening genomic libraries. The long range aim will be to characterize the RI genes in SHR and WKY to reveal any differences between them. This research project may have significance in elucidating the molecular basis for essential hypertension.